The invention relates to a drive which acts on both sides and for use in adjusting devices in motor vehicles. Thee invention is provided in particular for adjusting vehicle A seats or components such as back rests and seat cushions.
From DE 197 25 899 A1 a drive acting on both sides is known for generating rotary movement which starting from a zero position of a drive lever proceeds selectively into one or other drive direction whereby an element to be driven is only then turned when the drive lever is moved away from the zero position whilst the element which is to be driven is not entrained along when the drive lever is moved towards the zero position. The drive lever is able to swivel about a drive axis and is coupled to locking means which can be brought into engagement with teeth arranged around the circumference of a drive wheel. The locking means have a one-piece tilt element which tilts to and fro between two end positions depending on the relevant drive direction and in each end position the tilt element locks with the teeth of the drive wheel.
From DE 195 27 912 A1 a drive acting on both sides is known where a drive lever is mounted on a drive axle and supports swivel coupling elements whose free ends which are provided with toothed elements can be brought into engagement with the teeth arranged around the circumference of a drive wheel. The swivel coupling elements are associated with a slide guide which depending on the swivel direction of the drive lever lifts each relevant unstressed coupling element away from the teeth of the drive wheel. Spring areas are thereby provided on both sides outside of the slide guide and exert on the coupling elements a force directed against the engagement direction of the teeth so that so-called ratchet noises are avoided during movement.
The drives described have a relatively high number of individual parts which are expensive to manufacture and assemble. Similarly in the event of a xe2x80x9ctooth to toothxe2x80x9d setting of the coupling element and drive wheel this can lead to jumping across and to jerky movement on the drive lever and during resetting movement of the drive lever so-called ratchet noises can occur.
Starting from this prior art the object of the invention is to provide a drive acting on both sides to generate a rotary movement which uses a small number of individual parts, is simple to assemble, causes less noise during actuation and which can be coupled in any position and reset.
The solution according to the invention proposes coupling the drive wheel to the drive lever through a combination of at least one positive locking element having at least one associated elastic element. The elastic element can be deformed so that its contour matches the contour of the positive locking element whereby these two elements enter in engagement with each other. Through this positive engagement which can be produced with continuously variable adjustment the teeth of the coupling element are prevented from jumping over each other since a coupling always arises where the positive locking elements enter into engagement with the elastic element.
At the same time the provision of an elastic element, e.g. a volume or rubber elastic element ensures damping of the noises which occur during adjustment.
In one embodiment at least one elastic element is mounted on the drive wheel and positive locking elements are provided on the coupling elements wherein the positive locking elements deform the elastic element when torque is introduced through the coupling elements. This deformation is macroscopically contour-forming namely so that a force- or torque-transferring coupling is produced between the positive locking elements and the elastic element. The contour formation is thereby developed so that a sufficiently load-bearing coupling is produced between the positive locking element and the elastic element so that the drive wheel can be turned. In the region of the coupling between the positive locking elements and the elastic element it is thus possible to transfer forces acting in the circumferential direction of the drive wheel in order to generate rotation. The deformation of the elastic element ensures toothed engagement with the positive locking element so that it is possible to speak of a quasi positive locking connection.
In one embodiment, the positive locking elements are arranged on the drive wheel and the coupling elements are provided with the corresponding elastic elements whereby the end effect is that the same function is fulfilled. Which of the embodiments is better depends on the relevant field of use and the conditions and circumstances involved surrounding the manufacture of the drive.
The elastic elements on the output wheel or on the coupling elements are preferably fixed with positive engagement or material engagement on the drive wheel or on the coupling elements. This cuts down in particular the assembly work. In one embodiment, the elastic elements are made from polyurethane, but other elastic materials can also be provided such as e.g. rubber elastic materials or the material having the trade name xe2x80x9cVulkollanxe2x80x9d.
In one embodiment, the substantially rigid positive locking elements have the shape of teeth whereby each positive locking element can have one or more teeth. The configuration with only one tooth, or xe2x80x9cquasi one pin,xe2x80x9d projecting into the elastic element has the advantage of lower production costs but does bring the risk that the elastic element would become damaged owing to the deep penetration of the individual tooth. It is therefore proposed as an alternative to attach the positive locking element to several teeth so that the teeth can penetrate into the elastic element by a maximum of their tooth height. Several teeth furthermore have the advantage that the force is transferred evenly over a larger surface area of the elastic element.
In the event where the positive locking elements are mounted on the drive wheel they preferably have the shape of two concentric saw tooth like serrations whereby the steep flanks of each saw tooth like serration are aligned oppositely relative to each other.
In order to achieve a small idling path during the displacement of the drive lever, in a preferred configuration the coupling elements engage with the drive wheel when the drive lever is in the zero position; this means that the rigid positive locking elements and the elastic elements contact one another in the zero position and that in the event of torque transfer the loaded rigid positive locking element is reproduced in the elastic element.
In one embodiment, the coupling elements can be assigned a slide guide which lifts the unstressed coupling elements during movement of the drive lever from the zero position away from the drive wheel and keeps them raised until reaching the zero position once again. In this way, the unstressed coupling elements do not slide over the positive locking elements during the adjusting movement. Similarly, during the resetting movement of the drive lever the drive wheel is not entrained in the sense of the resetting movement.
In one embodiment, spring areas on either side outside of the slide guide areas exert a force against the engagement direction on the loaded coupling elements. The spring force is thereby measured so that when the drive lever is moved from the zero position the loaded coupling element remains in engagement with the drive wheel but during movement towards the zero position is brought out of engagement. During a resetting movement of the drive lever into the zero position, therefore, not one of the coupling elements is coupled with the drive wheel. The unstressed coupling element is brought out of engagement as a result of the slide guide areas and the stressed coupling element is uncoupled from the drive wheel as a result of the spring force of the spring area. During the resetting movement of the drive lever back into the zero position the elastic element and the positive locking elements are not in engagement with each other so that the resetting movement is made easier and the wear, more particularly on the elastic element, is reduced.
In one embodiment, the coupling elements in the zero position are not in contact with the drive wheel. Thus plastic deformation of the elastic element as a result of the permanent contact with the positive locking elements is prevented. A slide guide is associated with the coupling elements and, during movement of a drive lever out of the zero position, it brings the coupling element which is to be loaded into engagement with the drive wheel and ensures that during the opposite movement, thus when the drive lever is moved towards the zero position the unstressed coupling element remains out of engagement with the drive wheel.
In one embodiment, the smallest possible structural space is achieved by forming the slide guide in a cover element of the drive whereby a guide element is mounted on each coupling element and is guided in the corresponding slide guide. Depending on the arrangement of the cover element The guide element can protrude axially or radially from the coupling element whereby the slide guide is designed accordingly.
For a fast precise guide for the coupling elements, the guide elements can have a non-rounded corner section so that the coupling elements are quickly raised and rapidly moved into engagement with the drive wheel.